Ion concentration measuring device and ion concentration measuring element

Abstract

A crown ether derivative that acts as cation capturing ligand and alkanethiol having a longer carbon chain than a linker are immobilized, coexisting together, on the surface of a gold electrode, by using as the linker an insulating molecule (e.g., alkanethiol) that forms self-assembled monolayers. Electromotive force produced in association with cation coordination is measured by a potentiometer through a change in interfacial potential on the surface of the gold electrode. Further, an insulated gate field effect transistor formed on the same substrate as the gold electrode is used as the potentiometer. Furthermore, a straight-chain polymer physically adsorbed on the gold electrode is used in order to reduce the influence of the adsorption of impurities on the surface of the electrode during biological sample measurement.

Description

CLAIM OF PRIORITY[0001]The present application claims priority from Japanese application JP 2007-118640 filed on Apr. 27, 2007, the content of which is hereby incorporated by reference into this application.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an ion concentration measuring device for measuring a cation, particularly a sodium ion or a potassium ion, in a biological sample.[0004]2. Description of the Related Art[0005]Methods for analyzing the concentration of an electrolyte (such as a sodium ion or a potassium ion) in a biological sample, particularly blood serum or blood plasma, include flame photometry and ion selective electrode method. Of these, the ion selective electrode method is now widely used since it can determine ion concentration in a sample only by immersing the ion selective electrode in a sample solution in conjunction with a reference electrode. In the medical field, a device for the ion selective electrode ...

AI Technical Summary

Benefits of technology

This approach stabilizes the interface potential on the gold electrode, improves measurement accuracy, and expands the concentration-measuring range by reducing noise and drift caused by impurities, while maintaining the simplicity of immersion-based ion concentration measurement.

Problems solved by technology

The above-described ion selective electrode with the ligand immobilized on the surface of the gold electrode, however, is not designed in consideration of the insulating property of the surface of the gold electrode and the ligand's surrounding environment, and thereby takes impedance measurement rather than potential measurement to obtain a desired ion concentration.

The reason is that: the conventional ion selective electrode with the ligand immobilized on the surface of the gold electrode is not designed in consideration of the insulation property between the surface of the gold electrode and a measuring solution, and thus is incapable of stably measuring the interface potential because actual measurement is affected by leakage current at the surface of the electrode.

This makes it impossible to take the advantage of the conventional ion selective electrode method that the ion concentration in the sample is obtained only by immersing the ion selective electrode together with the reference electrode in the sample solution.

Moreover, the impedance measurement method also has the problem of a narrow concentration-measuring range in principle, because this method is a current measurement method.

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